Exactly. If you're worried about your portfolio halving, you're either too heavily invested in risky assets for the timeframe you wish to start drawing down, or

Exactly. If you're worried about your portfolio halving, you're either too heavily invested in risky assets for the timeframe you wish to start drawing down, or you're not and you need to stop looking at the day to day performance of financial markets. Your automatic order is just as likely to misfire and sell just before a recovery than it is to prevent you from losing everything. And worse, you need to realize that just because the markets have fluctuated, you haven't actually lost anything but paper value — you still own the same number of shares in the same number of companies. Selling those during a downturn is just cementing that loss in real dollars. And so say you've sold. That's only half the problem. Now you still need to figure out when to buy into the market again, unless you're planning on just hoarding the cash under your mattress.